import itertools
N=int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
A+=B
ans=0
a=list(itertools.permutations([i for i in range(N)])) 
b=list(itertools.permutations([i for i in range(N)]))
Z=len(b)
#print(a,b)
ANS=0
for i in range(Z):
    for k in range(Z):
        AT=0
        for j in range(N):
            if A[a[i][j]]>B[b[k][j]]:
                AT+=1
        if 2*AT>N:
            ANS+=1
print(ANS/(Z*Z))